sQuiddio
Global user-sourced and user-maintained repository of sailing destinations (marinas, anchorages, yacht clubs, docks, fuel stations etc.) available as waypoints in OpenCPN through a plugin.
Google Earth
Links a Google Earth satellite image to the area of chart being explored.
Celestial Navigation
Plugin to record Sextant Sights and show Circles of Position to obtain a Fix
Great Circle Route
A short introduction to to the Great Circle part of the Route Plugin. Route Plotting, Great Circle routes, Limited Circle Routes and Rhumb lines.
DR Dead Reckoning
Add DR positions to a GPX file exported from OpenCPN
oTCurrent
Display tidal current arrows for times other than the present
PhotoLayer
Display tidal current arrows for times other than the present
GE2KAP
Use GE2Kap to create Kap files which can be overlaid on Charts. (Companion software, not a plugin)